29 May 2015

CIS-60 HDR modem 35.5 Bd, π/8-DPSK8


CIS-60 is one of the Russian OFDM HDR (High Data Rate) Modem modes,  it uses 60 data carriers and 1 pilot carrier located 3300 Hz from dial frequency, as usual in CIS HDR modem series. According to my logs, CIS-60 comes in two waveforms (I have logged both the twos):
- Baudrate 30, modulation QPSK
- Baudrate 35.5, modulation π/8-DPSK8
in both the cases the carriers are 44.5 Hz spaced and the signals spreads a 2800 Hz bandwidth. Sometimes you could hear operators chatting (in voice) followed by a waveform switch, i.e. from DPSK-4 to DPSK-8: I do not know if it's for tests purposes or for some other reason. The original signal has been resampled to 8888.8 Hz.





radioscanner.ru reports CIS-60 DPSK-8 waveform here:
http://signals.radioscanner.ru/base/signal231/ 

25 May 2015

HFDVL modem: OFDM 73-tone (13 pilot tones) QPSK

(I-56578, ANgazu)


Total carriers: 73
Pilot carriers: 13
Data symbols per OFDM symbol: 60
Native sample rate (sps): 9600
FFT length (samples): 256
Modulation: QPSK
Bit rate (bps): 3600
Bandwidth (Hz): 2737.5
Samples per OFDM symbol: 320

OFDM parameters, body segment



The most interesting feature is the way the 13 pilot tones are formed, and why - at a first look - we found only 1 pilot tone (the higher one).

We found that all the even tones have QPSK modulation (at least into the seen signals) :


 and the top tone (the 73th) is clearly a pilot one:

  
We found that in the odd tones there is a new element in absolute constellation that generates a PSK8 pattern in diff constellation. We guess this element is a scattered pilot and, for some reason we do not know, it shifts diff constellation of 45 degrees, giving the false PSK8:


Skipping symbols, we could see the 'no modulated pilot' feature for these tones. Then, according to our analysis, the 13 pilots coule be formed in the following way:

- 1 fixed pilot tone (73th);
- 12 scattered pilots which are chosen in turn from 3 different sets (each set contains 12 odd tones);
(...and we are quite positive that we have exactly identified all the tones of each set).

The pilot tones configuration changes at every OFDM symbol: we do not know the reason (perhaps to contrast propagation conditions?) and the algorithm that determines the initial configuration; possibly the BPSK preamble has these data inside, but it's just a guess. Anyway, as said above, it looks like that all the odd tones are pilots-candidate (we could say “virtual pilots”) and only 12 of them are used - in turn - to form the real pilots, while the remaining 24 + the 36 even tones are used to transport user data (60 tones).
Here is an example of a possible pilot tones scheme that assumes the configuration A as the initial configuration:

configuration A (73th tone + 12 tones of the set-A)
configuration B (73th tone + 12 tones of the set-B)
configuration C (73th tone + 12 tones of the set-C)
...and so on, restarting from configuration A 

The trailing segment of the signal just exhibits all the odd (pilots candidate) tones, some using BPSK modulation.


Two words about the speed. Official documentation say:

Total carriers 73, Pilot carriers 13, Data symbols per OFDM symbol 60, Bit rate (bps) 3600 (assuming Bit rate to be the “system” speed “on the air”). Since the 30 baud PSK-4 modulation, the system grants 30 * 2 * 60 = 3600 bps data rate.

The HFDVL modem (waveform is developed by the groups "CeTIC" from the Universidad de Las Palmas de Gran Canaria and "GAPS" from Universidad Politécnia de Madrid, other than Aeropuertos Españoles y Navegación Aérea) has been heard mostly on USB 14350.0 and 14828.5 transmitting from Spain: we think that they are conducting tests that involve transmitters in two diferent sites which exchanges data. In one of our 14828.8 KHz recordings is quite clearly visible the different quality of the signals:

Emailing the HFDVL modem manufacturer, we got a confirm about what we were thinking: "[...]Yes, there are two modems transmitting and at this moment there are not other frequencies involved in the test."

21 May 2015

AT-3004D (CIS-12): MPSK 12-tones PSK-2, PSK-4 120 Baud


CIS-12 is a Soviet military pseudo OFDM 12-tones + 1 pilot tone modem allowing scrambled voice or data-communication at 120 Baud rate, modulation PSK-2 or PSK-4. CIS-12 is also known as MS5 or FIRE while the modem name is AT-3004D (or its newer counterpart  AT-3104).  
http://signals.radioscanner.ru/base/signal37/


"An interesting feature of these signals is that the sub-carriers are not orthogonal, since the manipulation speed is 120 Hz and channel spacing is 200: it means that each channel is formed separately, not as in OFDM using IFFT all at once, although the OFDM technology is used. CIS-12 modems may appear in three different variants, according to the n-ary PSK modulation: 2-PSK, 4-PSK offset (doesn't turn on 180^) and 4-PSK.Channels 1-10 are for user-data while 11 and 12 for the inspection. Accordingly, the aggregate information rate is 1200 and 2400 (PSK-2 and PSK-4)."

PSK-2 waveform:
 

PSK-4  waveform:
KarapuZ sent me a sample of this mode along with his comment:
"this mode modem is less resistant to interference, it is mainly used to transmit a surface wave, or at a distance of not more than one hop. A chance to hear him in Italy is very small".


 

19 May 2015

RUS-ARQ 100Bd/2000


FSK  ARQ system 100 Baud and 2000 Hz shift heard this morning (19 May) on 12129.5 cf starting from 0640, s/off at 0650. It sounds like an ARQ system, possibly from Russian Governative (then the nickname RUS-ARQ). As far as I know, the signal is sent by an outstation to its main 'home' station, that in its turn operates in CIS 3x100 (VFT 3 x FSK-2 channels) on three correspondents. All these stations (main and oustations) operate in synchronous mode, usually not far apart in frequency.

The recordered signal can be downloaded from here:
https://www.dropbox.com/s/wmkqgaw5s5ew7f2/19-May-2015-064925%2012.127500%20MHz.wav?dl=0



11 May 2015

UK modified WinDRM


British Military/Government OFDM 51-tone modem, a odified WinDRM waveform with no evidence of the three Pilot Tones which are one of the WinDRM features. Parameters are Br 37.5, Sh 46.8, modulation is QAM and QPSK each two (Pic. 1). 
It is an "ON/OFF" system with 53.33 mSec periods (ACF of 106.66 mSec as shown in Pic. 2), in this sample no info is sent apparently during the ON (data) periods. It's clearly visible that the "ON" segments are sent using all the 51 channels and are interspersed alternatively by the subsets of odd and even channels (Pic. 3)


Pic.1 modulation

Pic. 2 ACF value
Pic.3 symbol by symbol view

5 May 2015

Hagelin HC-256

14397.5 ---: unid 1440 Hagelin HC-256 voice scrambler, short QSO (23Apr15) 



The HagelinCryptos HC-265 is an analog dynamic synchronized voice scrambler.Preamble is transmitted on two FSK-2 channels, with periodic synchronization of every 400 milliseconds.

Thales Systeme-3000 Skymaster ALE

The signal reported here was heard on 2 May at 10.254.0 KHz on USB, around 0730z, and it is  Thales proprietary ALE protocol called Skymaster



The initial part of the signal - at first glance - uses PSK-4 (OQPSK) modulation at 2000 Baud speed and carrier frequency ~1600 Hz but it's likely an MSK modulation 2000Bd/1000: OQPSK and MSK are strictly connected and difficult to discriminate. The absolute phase variation diagram of this part it's a clue in favour of MSK.




The initial part is followed by short MFSK-8  125 Baud segment that is not compatible with MS 188-141 2G-ALE although the scope be the same.




The initial MSK part exhibits a 50ms ACF that corresponds to a 100-bit frame.


This proprietary waveform is used in their TRC-3500/TRC-3600 and TRC-3700 series radios.